1. Field of the Invention
The present invention relates to a nickel-M-alumina xerogel catalyst, a method for preparing the same, and a method for preparing methane using the catalyst.
2. Discussion of Related Art
In modern society, ensuring energy sources is an essential factor in terms of economic and industrial development. The importance of energy sources has increased in accordance with the rapid increase in energy consumption and the appearance of limitations on recoverable oil reserves. Also, the atmospheric pollution has become serious with a sudden increase in consumption of fossil energy. In developed countries such as several European countries and Japan, development of renewable energy technology has accelerated. Among fossil fuels, natural gas is a gaseous hydrocarbon naturally produced underground like petroleum. Natural gas is a fuel that contains methane (CH4) as a main component, and is clean enough to prevent environmental pollution, stable and convenient. Accordingly, natural gas has come into the spotlight as an alternative energy of a solid fuel such as petroleum, coal, etc. For this reason, natural gas has been widely used in various fields such as homes, commerce, transportation, and industries, and forms the basis of global energy industries together with petroleum and coal as an energy source which amounts to approximately ¼ of global energy consumption. In spite of an increase in the demand for natural gas, however, the supplies and prices are unstable due to limitations on recoverable natural gas reserves on the Earth and fluctuation of oil prices. To solve these problems, countries having low natural gas reserves have conducted much research on synthetic natural gas.
The term “synthetic natural gas” or “substitute natural gas” (SNG) refers to artificially produced natural gas. In recent years, there has been research conducted to prepare methane as a main component of natural gas from coal, biomass, or petroleum coke. Especially, a method of preparing synthetic natural gas from coal is expected to be a main energy source in the future in terms of stabilization of high prices of conventional natural gas using rich gas reserves and diversification of fuels.
Methods of preparing synthetic natural gas from coal include a method of obtaining methane by subjecting a synthetic gas obtained through coal gasification to a methane synthetic reaction using a catalyst (gasification method), a method of obtaining synthetic natural gas by allowing coal to directly react with hydrogen (hydrogasification method), and a method of obtaining synthetic natural gas by allowing coal to react with steam at a low temperature using a catalyst (catalytic gasification method).
The catalyst obtained according to the present invention is a catalyst used to synthesize methane from a synthetic gas obtained from coal through a gasification method. To perform a methanation reaction on the synthetic gas, research on various metal catalysts such as Ni, Re, Ru, Rh, Pt, Fe and Co has been conducted [M. V. Vannice, J. Catal., 37 vol., page 449 (1975)]. Among these, Ru and Co catalysts were reported to show the highest activities, but have a disadvantage in that their price competitiveness is very low. Ni has been commercially used due to price competitiveness and high reactivity, but has problems in that its reaction activity is lower than those of Ru and Co, and it may be deactivated by deposition and particle sintering reactions of carbon species as the reactions are in progress.
Also, the reactivity of a catalyst for a methanation reaction is highly affected by the kind of a carrier. So far, various kinds of supports such as Al2O3, SiO2, TiO2, La2O3 and CeO2 have been reported [S. Z. Ozdogan, P. D. Gochis, J. L. Falconer, J. Catal., 83 vol., page 257 (1983)]. Among these, Al2O3 has the highest thermal stability, and may enhance a yield of methane due to its proper interaction with an active metal.